Finally, we investigated strategic evolution on four empirical social networks that feature directed edges (Table REF ). These networks were assembled from empirical data on physical visitations among families in a Costa Rican town [1]}, surveys of friendship ratings on a University campus [2]}, the referral network among a sample of physicians in Illinois [3]}, and the follower-network among a sample of Twitter users [4]}. The proportion of unidirectional edges ranges from \(p=45\%\)  to \(p=80\%\)  in these empirical examples.
